STUDY LINKS COCAINE ADDICTION TO BIOLOGICAL CLOCK

WASHINGTON (Reuters) - Genes normally associated with an animal's internal
clock also may affect its ability to become addicted to cocaine, researchers
said Thursday.

Similar genes may play a role in human addiction, the researchers reported
in the journal Science, adding that the finding casts surprising new light
on the role of biological clocks.

"This opens up the field of drug studies to thinking about how a totally
unexpected set of genes function in response to drugs," Jay Hirsh, a
molecular geneticist at the University of Virginia who led the study, said
in a statement.

The findings even might explain why drugs such as cocaine keep people awake,
Hirsh said.

"These important findings illustrate that the clock genes perform other
important roles in regulating the physiology of fruit flies, and likely
humans," added Dr. Michael Sesma, a neurobiologist at the National Institute
of General Medical Sciences, whose institute helped fund the study.

Hirsh and colleagues were working with fruit flies -- tiny insects that,
like all other animals, share many of their genes with humans.

They looked at five known genes that affect the biological clocks in the
flies -- "period," "clock," "cycle," "doubletime" and "timeless." Flies that
lacked "period," "clock," "cycle" and "doubletime" did not become sensitized
to cocaine, the researchers said.

When animals or humans become sensitized to a drug, they require more and
more of it to have the same effect.

"Only those that lacked `timeless' had a normal response," Hirsh said in a
telephone interview.

Now his team will try to find out just what effects these genes have on
cells.

But there should be clear analogies to human addiction, he said, because
people possess versions of all five of these genes.

"We generally have three to four copies of every gene that a fly has a
single copy of," Hirsh said. "They have overlapping functions."

The research should shed light on a whole range of mental illnesses, Hirsh
said.

Knowing more about biological clocks also may help scientists explain why
people are more likely to have heart attacks in the morning and asthma
attacks at night, why some animals hibernate and why some people can wake up
at the same time every day without an alarm clock.